This invention relates to polyaspartic acid salt and more particularly to a process to form such salt.
Polyaspartic acid (PAA) salt is prepared by thermally polycondensing L-aspartic acid, optionally in the presence of acid catalyst, to form polysuccinimide (PSI) (sometimes interchangeably called anhydropolyaspartic acid or polyanhydroaspartic acid) and then reacting the PSI with aqueous alkali metal hydroxide to form a solution of PAA metal salt. This salt solution is industrially important for many uses such as a lubricant in metalworking applications or a corrosion inhibitor as disclosed in U.S. Pat. Nos. 4,971,724 and 5,401,428 to Kalota et al. The cost to ship salt to distant users could be significantly reduced if the water of solution was absent. Unfortunately, as the salt solution is dehydrated, a thick, viscous, gummy mass forms having the consistency of glue which is quite difficult to handle. Therefore, to the best of applicant's knowledge, heretofore such PAA polymer salt has been used in aqueous solution.